Roubini told Reuters that the Fed could even try to buy stocks to keep things afloat at some point:

"There might be a weak rally because people are being cheered by more quantitative easing by (Chairman Ben) Bernanke and the Fed, but if the economy is weakening, that is going to put downward pressure on earnings growth," said Roubini.

Roubini said the Federal Reserve may be pushed toward unconventional policy options as the stimulative effect of successive waves of quantitative easing - effectively printing money to buy government bonds - diminishes over time.

Unconventional policy could include "targeting the 10-year Treasury at 1 percent, doing credit easing rather than quantitative easing, targeting nominal GDP, price-level targeting and lots of stuff that is more esoteric," said Roubini. "Eventually if everything goes wrong, they can even buy equities."

Roubini thinks things will at least hold together through November, when presidential elections take place in the United States:

I think Greece is not going to exit until November. Things are not going to blow up until after November. Everybody is kicking the can down the road. We are kicking the can down the road on our fiscal issues. China is kicking the can down the road on their own structural issues because of a changing leadership. The Europeans want to avoid pulling the plug on Greece until maybe next year. We are not going to have a war with Iran until after the election...next year is the time where the can becomes too big to kick it down, and it hits a big, thick brick wall, and then we have a global perfect storm.